1. Field of the Invention
This invention relates to an apparatus for receiving a multiple signal transmitted by multiplexing an ordinary television signal and other video signals and for reproducing the video signals from the multiple signal, or more in particular to a recording apparatus in a still-picture reproduction system, whereby a still-picture video signal divided for every several horizontal scanning lines and inserted in the vertical fly-back period of an ordinary television signal included in a multiple signal received is extracted from the multiple signal and recorded for reproduction and, upon completion of the recording of the video signal in an amount sufficient to form a picture, the video signal is repeatedly read out for reproduction.
2. Description of the Prior Art
Recently, communication systems intended to meet a great variety of demands in the field of information service have been suggested. The still-picture multiplex transmission system is one. According to this system, a still-picture video signal is superposed on a currently used television broadcast signal in such a manner as not to interfere with the receiving of the other pictures by the current television receiver.
Such a still-picture multiplex transmission system will be briefly described below. In an example of the still-picture multiplex transmission system, a video signal carrying a still-picture and independent of an ordinary television signal is inserted at a proper position in the waveform of the ordinary television signal, for example, at a proper position in the vertical fly-back period not interferring with the operation of the conventional receiver. The 14th to 16th lines, and the 277th to 279th lines of the horizontal scanning period are one example of the position selected for insertion of the still-picture video signal. By so doing, it is possible to transmit three lines of video signal superposed for each field. (The resultant signal will be herein referred to as a still-picture multiplexed signal.) At the receiving end, the still-picture video signal inserted at a predetermined position of the television signal is extracted and written in such a memory or recorder as a magnetic disc recorder and, upon completion of the writing of the video signal representing a picture, the stored signal is read repeatedly thereby to reproduce the still-picture. The waveforms into which the still-picture video signal superposed on the ordinary television signal is divided for predetermined parts of the horizontal scanning period are identical with that of each line of the ordinary television signal. A control signal required for separating the video signal from the received still-picture multiplexed signal is inserted in the part of the still-picture video signal corresponding to the vertical fly-back period.
The indication on an indicating means such as used with the television receiver, of the still-picture video signal extracted from the still-picture multiplexed signal and stored in the recorder requires horizontal and vertical synchronizing signals. As such a horizontal synchronizing signal, the horizontal synchronizing signal of the ordinary television signal may be commonly used. The superposed video signal, however, should not carry the vertical synchronizing signal for its own. This is because, if the vertical synchronizing signal is added to the still-picture video signal, the fact that a vertical synchronizing signal different from the vertical synchronizing signal of the ordinary television signal is added thereto at a different position in the ordinary television signal adversely affects the vertical deflection circuit of the receiver receiving the ordinary television signal. And the receiver reproducing a still-picture must be additionally provided with a vertical synchronizing signal-generating circuit and a vertical synchronizing signal-adding circuit for adding another vertical synchronizing signal different from the original standard vertical synchronizing signal to the video signal stored in the memory, using the control signal as a reference. The vertical synchronizing signal-adding circuit, in which the DC level of the signal supplied from the vertical synchronizing signal-generating circuit is required to be rendered strictly identical with that of the video signal to which the vertical synchronizing signal is to be added, must be inconveniently adjusted.